1. Field of the Invention
The present invention relates to a method and an apparatus for recording an image, and more particularly to a method and an apparatus for recording an image wherein image data on an image divided into a plurality of picture elements or pixels are written in a memory, and the image data written therein are read sequentially so as to record the image on the basis of the image data read.
2. Description of the Related Art
Optical beam scanners have hitherto been proposed for effecting reading or recording stably and at high speed by means of a plurality of laser beams by using an optical modulator constituted by a multi-frequency acousto-optic modulator (AOM) (Japanese Patent Application Publication No. 5741/1988, Japanese Patent Application Laid-Open Nos. 5455/1979 and 41618/1982, Japanese Patent Application Publication No. 9856/1978, etc.).
In the optical beam scanner, such as a laser beam recording apparatus, for recording an image by using the AOM, a laser beam made incident in response to an inputted signal is divided into a plurality of laser beams by the AOM, and the plurality of laser beams are simultaneously applied to a photosensitive surface so as to record an image. At that time, plane scanning is effected by performing main scanning as well as sub scanning in a direction perpendicular to that of main scanning, using the laser beams by means of a scanning optical system comprising a rotating polygon mirror, a galvanometer mirror, and the like.
Here, image data representing the presence or absence of a record at each pixel for forming the image is inputted to the AOM, the application of the laser beams is subjected to on-off control on the basis of the image data while the scanning is being effected with the laser beams.
Accordingly, the main scanning of a plurality of lines are effected simultaneously as the plurality of laser beams are reflected by reflecting surfaces of the polygon mirror which rotates at high speed. When this main scanning is effected, the application of the laser beams is subjected to on-off control such that pixels based on the inputted image data will be recorded on a photosensitive material, thereby forming portions of the image corresponding to the main scanning lines along the loci of the laser beams. Upon completion of the main scanning with the laser beams, the laser beams reflected by the polygon mirror are reflected by the galvanometer mirror which is rotated at a predetermined speed, thereby effecting the sub scanning. As a result of this sub scanning, ends of groups of laser beams constituted by the plurality of laser beams are connected together without any gaps, thereby forming the image. It should be noted that there are cases where the main scanning and the sub scanning are effected simultaneously.
For instance, in a case where characters are recorded, the recorded data on the characters are sequentially inputted to the laser beam recording apparatus from an input device of a host computer or the like. The inputted characters are set as font data comprised of a set of pixels corresponding to recording positions, and are sequentially stored in a memory with respect to each inputted character, thereby forming image data corresponding to one recorded image plane. Image data of a predetermined bit length are sequentially read from the memory in which these image data are stored. Then the image data thus read are sent to a recording system, and the application of the laser beams is subjected to on-off control on the basis of the image data read.
However, in the case where the image data are sequentially stored in the memory and the stored image data are read from the memory, as described above, it is necessary to store and read the image data for each predetermined area, i.e., the image data of a predetermined bit length. Therefore, the time duration for writing the image data into the memory and the time duration for reading the same from the memory correspond to the write processing time and the read processing time of the memory, respectively. To reduce these processing times, it is necessary to use a device whose processing speed is fast. In addition, although it is conceivable to reduce the processing time of an essential portion by using a device whose time duration for writing into the memory differs from the time duration for reading from the memory, as required, the arrangement of the apparatus becomes complicated. In this case as well, since the image data for a predetermined area, i.e., the image data of a predetermined bit length, are read, the reduction of the processing time is dependent upon the capacity of the device. Hence, there are naturally limitations to the reduction of the processing speed.